push rod issue

[coreaw]

I have a '68 with the 200cui 6 the engine ran perfectly until I decided to put a new headliner in it and the car had to sit for a prolonged period of time. When I finally restarted it it blew the head gasket and ever since I replaced the head gasket I have had issues with the push rods coming off the rocker arm. There's no warning to it and I have fixed it twice now but I can't figure out why they keep coming off. It doesn't look like there's any adjustment to be made on the rocker arms but I could be wrong. I don't know if anybody has had this happen before and if they have any tips. I just want my old mustang back. Also, I just moved to Lynchburg Virginia and am looking for a good reliable mechanic to bring the car too if anyone has any suggestions.